Nanoparticle carrier platform and methods for controlled release of subterranean well treatment additives

ABSTRACT

Nano-sized mixed metal oxide carriers capable of delivering a well treatment additive for a sustained or extended period of time in the environment of use, methods of making the nanoparticles, and uses thereof are described herein. The nanoparticles can have a formula of:A/[Mx1My2Mz3]OnHmwhere x is 0.03 to 3, y is 0.01 to 0.4, z is 0.01 to 0.4 and n and m are determined by the oxidation states of the other elements, and M1 can be aluminum (Al), gallium (Ga), indium (In), or thallium (Tl). M2 and M3 are not the same and can be a Column 2 metal, Column 14 metal, or a transition metal. A is can be a treatment additive.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/811,128, filed Mar. 6, 2020, which a continuation of U.S. patentapplication Ser. No. 15/897,250 (U.S. Pat. No. 10,619,086), filed Feb.15, 2018, which is a divisional of U.S. patent application Ser. No.15/593,603 (U.S. Pat. No. 9,926,485), filed May 12, 2017, which claimsbenefit to U.S. Provisional Application No. 62/345,568, filed Jun. 3,2016, all of which are incorporated herein by reference in theirentirety and without disclaimer.

BACKGROUND OF THE INVENTION A. Field of the Invention

The invention generally concerns nanoparticle carrier platforms tocontrollably release well treatment additives (e.g., scale inhibitors)to subterranean gas, oil, or water wells, or subterranean formations.The nanoparticles can be made of a mixed metal oxide formed as a crystallattice structure. Subterranean well treatment additives can be loadedonto the surface or impregnated within the nanoparticles.

B. Description of Related Art

Chemical carrier platforms can be used in the subterranean drillingindustry to deliver subterranean well treatment additives. By way ofexample, scale inhibitors can be injected into the subterranean well totry to extend the time period over which such additives are released.Controlled or extended release of additives from the carrier platformsis desirable in order to avoid or eliminate retreatment of the well, asretreatment is costly and time consuming.

There are also safety and environmental risks involved with eachtreatment. In particular, scale inhibitors used to prevent or to controlscale depositions in subterranean wells can be delivered by a processknown as a “squeeze treatment”. In scale-inhibitor squeeze, theinhibitor can be attached to the formation matrix by chemical adsorptionor by temperature-activated precipitation and returns with the producedfluid at sufficiently high concentrations to avoid scale precipitation.Scale inhibitor chemicals can be continuously injected through adownhole injection point in the completion, or periodic squeezetreatments can be undertaken to place the inhibitor in the reservoirmatrix for subsequent commingling with produced fluids. Some scaleinhibitor systems integrate scale inhibitors and fracture treatmentsinto one step. In this type of treatment, a scale inhibitor can bepumped into the formation, adsorbs to the matrix during pumping and thenrelease when the fracture begins to produce water. As the water passesthrough the inhibitor-adsorbed zone, it dissolves the inhibitor toprevent scale nucleation and deposition of salts in the well. Acommercially available scale inhibitor system is sold under the nameScaleguard® (from Carbo Ceramics, Inc., Houston, Tex.). This systemincludes a porous ceramic proppant impregnated with a scale inhibitorwhich releases the scale inhibitor upon contact with water for slowrelease in fractured wells via a semipermeable coating.

Various scale inhibitors systems have been investigated to improve thedelivery of additives to a hydrocarbon producing well. By way ofexample, Shen et al. (SPE International Oilfield Scale Conference.Society of Petroleum Engineers, 2008) describescalcium-diethylenetriamine penta(methylenephosphonate) (Ca-DTPMP)nanoparticle suspensions for the controlled placement of scaleinhibitors in a formation and transport of the scale inhibitors in aporous medium. Boehmite based sulfonated polymer nanoparticles have beendescribed by Yan et al. (Offshore Technology Conference. OffshoreTechnology Conference, 2013), while the production of nano-sizedboehmites for phosphate sorption has been described by Wantanbe et al.(Separation Science and Technology 46.5 (2011): 818-824).

Other attempts to improve release of scale inhibitors into a wellinclude crosslinking polymeric scale inhibitors with aluminum oxidehydroxide (AlO(OH)) or α-aluminum oxide hydroxide (α-AlO(OH)) (See, forexample, Yan et al. SPE International Symposium on Oilfield Chemistry,Society of Petroleum Engineers, 2013 and Yan et al. SPE Journal 19.04(2014): 687-694). Zhang et al. describes crystalline phasecalcium-phosphonate scale inhibitor nanomaterials prepared fromamorphous silica templated calcium-phosphonate precipitates (RSC ADV.2016, 6, 5259-5269 and Ind. Eng. Chem. Res. 2011, 50(4), pp. 1819-1830).

Still further, other additives have been combined with scale inhibitorsfor well treatment. By way of example, antimicrobial compositions incombination with scale inhibitors made from various possiblecombinations of metal oxides is described in U.S. Pat. No. 7,422,759 toKepner et al.

Despite the foregoing, the above mentioned nanoparticle carriers sufferfrom inadequate controlled release of the subterranean treatmentadditives over an extended period of time from the currently availablecarrier platforms, leading to the need for retreatments, increasedenvironmental risks, and economic losses.

SUMMARY OF THE INVENTION

A discovery has been made that solves the problems associated withtreating subterranean formations (e.g., reservoirs) or wells (e.g., oil,gas and water wells) with well treatment additives (e.g., scaleinhibitors). The solution resides in the development of a mixed metaloxide nanoparticle, preferably a ternary mixed metal oxide nanoparticlethat is loaded with a well treatment additive. The nanoparticle can havea general structure of A/[M¹ _(x)M² _(y)M³ _(z)]O_(n)H_(m) where M¹, M²,and M³ are in the crystal lattice structure of the nanoparticle, and Ais the well treatment additive that can be slowly released from thenanoparticle. Surprisingly, this structural set-up allows for a slowrelease profile of the additive, such that the additive can be releasedfrom the nanoparticle over an extended period of time (e.g., at leastfor 10 days to 10 years or more, 500 days, at least for 1000 days, atleast for 2000 days, at least for 500 days to 2500 days, or at least for500 days to 2000 days after well treatment) during use. The time thenanoparticle continues to return meaningful concentrations of inhibitorcan vary depending on the water production rate of the well. This, inturn, reduces the costs, expenses, and overall inefficiencies withhaving to perform continuous or more periodic well treatments such aswith the processes currently used in the well-treatment industry.Without wishing to be bound by theory, it is believed that by having themetals of the mixed metal oxide nanoparticle present in the crystallattice, more efficient loading (e.g., adsorption or chemical bonding)of the well treatment additive into the crystal lattice can take place.Such loading can provide for a more controllable or slower dissolutionor desorption of the additive into an aqueous environment and inhibitleaching of the treatment additive from the nanoparticle, therebyproviding the prolonged release profile of the additive during use.

In one aspect of the present invention, there is disclosed nanoparticlesof general formula A/[M¹ _(x)M² _(y)M³ _(z)]O_(n)H_(m), where A is thesubterranean treatment additive (e.g., a scale inhibitor) and [M¹ _(x)M²_(y)M³ _(z)]O_(n)H_(m) is a mixed metal oxide in the form of a crystallattice structure, which includes various loadings of the three metals.The nanoparticle can include aluminum oxyhydroxide (AlOOH) or aluminumhydroxide (Al(OH)) phases. Subterranean treatment additive, and welltreatment additive can be used interchangeably throughout thespecification. M¹ can be a metal from Column 13 of the Periodic Table(e.g., aluminum (Al), gallium (Ga), indium (In) and titanium (Ti). M²and M³ can each be a Column 2 metal, a Column 14 metal, or a transitionmetal of the Periodic Table. In a preferred instance, M² and M³ aredifferent from each other. The amount of oxygen present in the crystallattice can be determined by the oxidation states of the metals suchthat a balanced electric charge (i.e. of zero) is achieved. Said anotherway, the crystal lattice structure formed by the three metals and theoxygen preferably maintains a neutral charge. It was surprisingly found,as described in one non-limiting embodiment in the Examples section,that such nanoparticles provide controlled release of the subterraneanwell treatment additive over an extended period of time, which canreduce or eliminate the need for reapplication of the additive,providing significant cost and labor savings. By way of example, thenanoparticles of the present invention provided scale inhibitor for 2000days as compared to 215 days for a conventional scale inhibitor (e.g.,sulfonated polycarboxylic acid (SPCA)). The nanoparticles can have aparticle diameter of up to 10,000 nm, and are preferably in the 10-200nm size range as determined by laser particle size analysis andtransmission electron microscopy (TEM). The nanoparticle diameter canalso range from, e.g., 1 to 1000 nm, from 5 to 700 nm, from 10 to 500nm, from 50 to 300 nm, or any value or range from 1 nm up to 10,000 nm.

In preferred aspects, the present invention relates to nanoparticlesthat allow for extended release of subterranean well treatmentadditives, e.g., scale inhibitors. As discussed above and throughout thespecification, the additive can be bound to the nanoparticle orotherwise adhered to the nanoparticle. The additive can be a scaleinhibitor that is an organic molecule having a carboxylic acid, apolycarboxylic aspartic acid, maleic acid, sulfonic acid, phosphonicacid, or a phosphate ester group. In particularly preferred embodiments,the scale inhibitor can be a polymer that includes sulfonatedpolycarboxylic acid groups.

Also disclosed are methods of producing the nanoparticles. The methodcan include obtaining an aqueous solution of an alkoxide, andprecipitating the nanoparticle having M¹, M² and M³ in the crystallattice of the nanoparticle. The subterranean well treatment additivecan then loaded onto the nanoparticle. In a preferred aspect, theprecipitation step can be performed by reducing the pH, or it caninclude removing the alkoxide from the aqueous solution, as well as,optionally, water. In preferred aspects, the solution can contain 0.01to 9 wt. % M¹, from 0.01 to 1 wt. % M² and M³.

Another aspect of this invention is a subterranean well treatmentcomposition containing the nanoparticles of the present invention, andmethods of treating the well with such composition by injecting it intoa well or a subterranean formation (e.g., a reservoir or an uncasedwell). The composition may be added to other drilling fluids, e.g.,saltwater or other aqueous fluids. The composition can include aqueous,nonaqueous medium, or mixtures thereof (e.g., salt water, an acidicaqueous solution, low sulfate seawater, an aqueous sodium carbonatesolution, a surfactant, or other flush fluid, oil phase, suspension,non-aqueous delivery, or any combination thereof).

In some embodiments, a method of delivering an additive to asubterranean formation is disclosed. The method can include obtaining acomposition that includes the additive loaded nanoparticles describedabove and throughout the specification and providing the additive loadednanoparticle composition to a subterranean formation. The additiveloaded nanoparticle composition can be provided to a drilling fluid (mudfluid) or an enhanced oil recovery fluid.

The following includes definitions of various terms and phrases usedthroughout this specification.

The term “capable of being released” as it relates to the subterraneanwell treatment additive means that, under conditions of use, e.g., in asubterranean well, the well treatment additive dissociates, hydrolyzes,is chemically unbound, or becomes otherwise separated from thenanoparticle and available for use for its intended purpose, e.g., ascale inhibitor in a subterranean well.

The term “controlled release over an extended period of time” relates tothe release rate of the subterranean well treatment additive from thenanoparticles and means that the additive is, in an environment of usesuch as, e.g., a subterranean well, released from the nanoparticle overa longer period of time than if the additive were not adsorbed orotherwise affixed to the to the nanoparticle of the invention.

The terms “formation fluid” or “formation fluids” includes liquids andgases present in a formation. Non-limiting examples, of formation fluidinclude hydrocarbon liquids and gases, water, salt water, sulfur and/ornitrogen containing hydrocarbons, inorganic liquids and gases and thelike.

The terms “about” or “approximately” are defined as being close to asunderstood by one of ordinary skill in the art. In non-limitingembodiment, the terms are defined to be within 10%, preferably within5%, more preferably within 1%, and most preferably within 0.5%.

The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, ormolar percentage of a component, respectively, based on the totalweight, the total volume of material, or total moles, that includes thecomponent. In a non-limiting example, 10 grams of component in 100 gramsof the material is 10 wt. % of component.

The term “substantially” and its variations are defined to includeranges within 10%, within 5%, within 1%, or within 0.5%.

The terms “inhibiting close” or “reducing” or “preventing” or “avoiding”or any variation of these terms, when used in the claims and/or thespecification includes any measurable decrease or complete inhibition toachieve a desired result. The term “effective,” as that term is used inthe specification and/or claims, means adequate to accomplish a desired,expected, or intended result.

The use of the words “a” or “an” when used in conjunction with any ofthe terms “comprising,” “including,” “containing,” or “having” in theclaims, or the specification, may mean “one,” but it is also consistentwith the meaning of “one or more,” “at least one,” and “one or more thanone.”

The nanoparticles and methods of the present invention can “comprise,”“consists essentially of,” or “consists of” particular elements,ingredients, components, compositions, etc. disclose throughout thespecification. With respect to the transitional phrase “consistingessentially of,” in one non-limiting aspect a basic and novelcharacteristic of the nanoparticles of the present invention are theirability to deliver a controllable release well treatment additive overan extended period of time during use (e.g., in subterranean wells).

The words “comprising” (and any form of comprising, such as “comprise”and “comprises”), “having” (and any form of having, such as “have” and“has”), “including” (and any form of including, such as “includes” and“include”) or “containing” (and any form of containing, such as“contains” and “contain”) are inclusive or open-ended and do not excludeadditional, on recited elements or method steps.

Other objects, features and advantages of the present invention willbecome apparent from the following figures, a detailed description, andexamples. It should be understood, however, that the figures, detaileddescription, and examples, while indicating specific embodiments of theinvention, are given by way of illustration only, and are not meant tobe a limiting. Additionally, it is contemplated that changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a method to treat a subterranean well using thenanoparticles of the present invention loaded with a subterraneantreatment additive.

FIG. 2 is a graph of nanoparticle size in micrometers versus volumedensity in percent.

FIG. 3 depicts a transmission electron microscopy (TEM) image of theSPCA loaded nanoparticles at a 100 nm s

FIG. 4A shows XRD patterns for the Al₁(Mg_(0.02)Ca_(0.02))OOH with theAlOOH phase being identified by the square monikers and residual sodiumchloride being identified by the circle monikers.

FIG. 4B shows XRD patterns for the Al₁(Mg_(0.02)Ca_(0.02))OOHnanoparticle and a comparative sample without Ca/Mg addition.

FIG. 4C is an XRD spectra curve fit data of FIG. 4B.

FIG. 5 is a scanning electron image of the Al₁(Mg_(0.02)Ca_(0.02))OOHnanoparticle of the present invention.

FIG. 6 is are plots of initial and final Total Al concentration (M) vs.pH, assuming boehmite as possible precipitation and total Mg vs. pH,assuming brucite as possible precipitation at 90° C.

FIG. 7 depicts graphs of production time in days versus SPCAconcentration in mg/L in produced water for SPCA alone and loadednanoparticles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A discovery has been made which provides nanoparticulate carriers forsubterranean treatment additives (e.g., well treatment additives). Thesenanoparticulate carriers can provide extended or sustained release of asubterranean treatment additive in an environment of use, e.g., in asubterranean oil, gas well, water well, or any subterranean reservoir.Controlled release of such additives over an extended period of timedecreases or eliminates the need to retreat wells or subterraneanformations (e.g., hydrocarbon reservoirs) with such additives, providinga cost and labor savings, and less environmental risks. The discovery ispremised on bonding or adsorbing the additive to nanoparticles of mixedmetal oxides. These nanoparticulate carriers can be prepared by: (1)obtaining an aqueous solution that includes a metal (M¹) alkoxide, aswell as a second and third metal salt or alkoxide (M² or M³ salt oralkoxide); (2) precipitating from the aqueous solution a nanoparticlehaving M¹, M², and M³ in the crystal lattice structure of thenanoparticle; and (3) loading the subterranean treatment additive (e.g.,well additive) into the nanoparticle.

The invention provides an elegant way to provide a cost- andlabor-effective methods to deliver subterranean treatment additives suchas scale inhibitors to wells so that they release the additive over along period of time, in a manner that reduces or eliminates the need toretreat wells with such additives. The invention also provides effectivemethods to deliver additives to fluids used to produce fluids (e.g., oiland gas) from subterranean formations. For example, delivery ofadditives to drilling fluid additives (mud additives), enhanced oilrecovery (EOR) fluids, or the like.

These and other non-limiting aspects of the present invention arediscussed in further detail in the following sections.

A. Nanoparticles with a Subterranean Treatment Additive

The subterranean treatment additive containing nanoparticle (“loadednanoparticle”) of the present invention is a mixed metal oxidenanoparticle having the subterranean treatment additive connected to thenanoparticle such that small, but effective, amounts of subterraneantreatment additive are removed from the nanoparticle over a period oftime. The loaded nanoparticles are discussed in further detail in thefollowing sections.

1. Mixed Metal Oxide Nanoparticulate Carrier

The nanoparticles of the present invention can include a mixed metaloxide of three metals M¹ M² and M³. These metals can form the crystallattice of the mixed metal oxide. M¹ metals can include Column 13element of the Periodic Table. Non-limiting examples of Column 13 metalsinclude aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). M²and M³ metals can include a Column 2 metal, a Column 14 metal, or atransition metal of the Periodic Table. Non-limiting examples of Column2 metals include beryllium (Be) magnesium (Mg), calcium (Ca), strontium(Sr), barium (Ba), or radium (Ra). Non-limiting examples of Column 14metals include tin (Sn), lead (Pb), Germanium (Ge). Non-limitingexamples of transition metals (Columns 3-12) include scandium (Sc),titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe),cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium(Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru),rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf),tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir),platinum (Pt), gold (Au), mercury (Hg), rutherfordium (Rf), dubnium(Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), meitnerium (Mt),darmstadtium (Ds), roentgenium (Rg) and copernicum (Cn).

The nanoparticles of the present invention can have the general formula:A/[M¹ _(x)M² _(y)M³ _(z)]O_(n)H_(m)where A is a subterranean well treatment additive capable of beingreleased from the nanoparticle, and M¹, M², and M³ are in the crystallattice structure of the nanoparticle. M¹ is a Column 13 element can bealuminum (Al), gallium (Ga), indium (In), thallium (Tl). M² and M³ canbe Column 2 metal, a Column 14 metal, or a transition metal, with theproviso that M² and M³ are different. M² and M³ can each independentlybe beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium(Ba) and radium (Ra), or combinations thereof. In a particularembodiment, Mg and Ca are particularly preferred, especially when M¹ isaluminum (Al). The molar amounts of each metal are designated by x, y,and z, with x ranging from 0.03 to 3, y ranging from 0.01 to 0.4, and zranging from 0.01 to 0.4. The molar amount of oxygen is represented byn, and the molar amount of hydrogen is represented by m. The molaramount of oxygen is determined by the oxidation states of the metals M¹,M², and M³ and the molar amount of hydrogen is determined by hydrolysisof metals M¹, M², and M³ in the crystal lattice. According to thepresent invention, x can range from 0.03 to 3, 0.5 to 1, 2 to 3, or0.03, 0.05, 0.1, 0.15, 1.0, 1.05, 1.1, 1.15, 2.0, 2.05, 2.1, 2.15, 3.0or any value or range there between, y and z can range from 0 to 0.4,preferably from 0.1 to 0.3, and more preferably from 0.1 to 0.2, or0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or any value or rangethere between, n can range from 1 to 10, more preferably from 2 to 8,and most preferably from 3 to 5, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, orany value or range there between, and m can range from 1 to 5, morepreferably from 1 to 4, and most preferably from 1 to 3, or 1, 2, 3, 4,5, or any value or range there between. Without wishing to be bound bytheory, it is believed that the amount of hydrogen can be related to thedegree of hydrolysis. In a partially hydrolyzed crystal, which is theboehmite phase, the molar concentration of O is twice as much ashydrogen, thus n=2 m. In fully hydrolyzed crystal, which is thehydroxide phase, the molar concentration of O is equal to that ofhydrogen, thus n=m. In some embodiments the a oxyhydroxide or hydroxideis not present and the nanoparticle has the general structure of A/[M¹_(x)M² _(y)M³ _(z)]O_(n), where x, y, z, and n are as defined above.

The nanoparticles can have an atomic ratio of metals ranging from about1 to about 99. For example, in one aspect the atomic ratio of a M¹/M²/M³can range from 20-80:20-60:20-80, or 40-75:25-60:25-60, preferably90:5:5, 60:30:10, 60:25:15, 50:25:25, 50:30:20, 40:50:10 or any ratiothere between. In another aspect, the atomic ratio of a Al/Mg/Cananoparticle can range from about 20-80:20-60:20-80, or40-75:25-60:25-60, preferably about 60:30:10, about 60:25:15, about50:25:25, about 50:30:20, about 40:50:10, and about 90:5:5 or any rangethere between. The ratio of oxygen to the metals will depend primarilyon the oxidation state of the metals and can vary accordingly. Thenanoparticles can include aluminum oxyhydroxides (α-AlOOH, β-AlOOH, orγ-AlOOH) or aluminum hydroxides phase (Al(OH)₃), either amorphous orcrystallized phases.

The nanoparticles of the present invention have physical properties thatcan contribute to the controlled release of the subterranean welltreatment additive over an extended period of time. The nanoparticlescan have an average diameter of from 1 nm to 10,000 nm, preferably 10 nmto 200 nm in diameter, and more preferably from 15 to 175 nm, 2 to 12 nmor 5 nm to 10 nm, or 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10nm, 11 nm, 12 nm or any range or value there between as measured bylaser particle size and TEM.

2. Subterranean Treatment Additive

Subterranean treatment additives are additives that can effect orinhibit performance of a material or fluid in a subterranean well,reservoir, or the like. The subterranean treatment additive can beseparated from the nanoparticle in response to a stimuli (e.g.,formation fluid, water, or pressure). The additive can be bound to thenanoparticle, e.g., chemically via an ionic bond, and/or be adhered tothe nanoparticle. Non-limiting examples of the nanoparticle bonding tothe additive include an ionic bond, a covalent bond, a hydrogen bond, aVan der Walls interaction. Adhesion to the nanoparticle can be throughabsorption or adsorption onto the particle.

Non-limiting examples of a subterranean treatment additive include ascale inhibitor, a hydrate inhibitor, a clay stabilizer, a bactericide,a salt substitute, a relative permeability modifier, a sulfidescavenger, a corrosion inhibitor, a corrosion inhibitor intensifier, apH control additive, a surfactant, a breaker, a fluid loss controladditive, an asphaltene inhibitor, a paraffin inhibitor, a chelatingagent, a foaming agent, a defoamer, an emulsifier, a demulsifier, aniron control agent, a solvent, a friction reducer, or any combinationthereof. A scale inhibitor is a particularly preferred subterranean welltreatment additive. The scale inhibitor can be an organic molecule(e.g., a polymer, oligomer, copolymer, and the like) having afunctionalized group that can bind to the particle. Non-limitingexamples of functionalized groups include a carboxylic acid, apolycarboxylic acid, aspartic acid, maleic acid, sulphonic acid,phosphonic acid, or a phosphate ester group or salts thereof. Aparticularly preferred scale inhibitor is a polymer containingsulfonated polycarboxylic acid groups (e.g., SPCA). A non-limitingexample of a commercial source of SPCA is Nalco Champion an Ecolabcompany (USA) sold under the tradename EC6157A.

B. Methods of Making Nanoparticles

The nanoparticles of the present invention can be prepared by aco-precipitation method. The subterranean treatment additive can then beadded to the nanoparticle using impregnation or coating methods. Thesemethods are described in more detail below and in the Examples section.The co-precipitation method can include the steps of: obtaining anaqueous solution of an M¹ alkoxide, an M² salt or alkoxide, and an M³salt or alkoxide; and precipitating from the aqueous solution ananoparticle having M¹, M², and M³ in the crystal lattice structure ofthe nanoparticle.

In step one of the method, an aqueous solution of an M¹ alkoxide, an M²salt or alkoxide can be obtained. The aqueous solution can contain from0.01 to 9 wt. % M¹, 0.1 to 7.5 wt. % M¹, 1.0 to 5 wt. % M¹, or 2 to 3wt. % M¹, 0.01 to 1 wt. % M², from 0.1 to 0.5 wt. % M², or from 0.25 to0.3 wt. % M², and contains from 0.01 to 1 wt. % M³, from 0.1 to 0.5 wt.% M³, or from 0.25 to 0.3 wt. % M³.

Non-limiting examples of alkoxides that can bond to M¹, M², and/or M³include methoxide, ethoxide, propoxide, isopropoxide, s-butoxide,i-propoxide, 2-ethylhexoxide, t-butoxide, hexafluoro-t-butoxide, tri-secbutoxide or combinations thereof. In particularly preferred aspects, M¹alkoxide can be aluminum tri-sec-butoxide.

M² and M³ metals can be provided in varying oxidation states asmetallic, oxide, hydrate, or salt forms typically depending on thepropensity of each metals stability, reactivity, and/orphysical/chemical properties, and are preferably provided aswater-soluble salts or alkoxides. The metals in the preparation of thenanoparticles can be provided in stable oxidation states as complexeswith monodentate, bidentate, tridentate, or tetradentate coordinatingligands such as for example iodide, bromide, sulfide, thiocyanate,chloride, nitrate, azide, acetate, fluoride, hydroxide, oxalate, water,isothiocyanate, acetonitrile, pyridine, ammonia, ethylenediamine,2,2′-bipyridine, 1,10-phenanthroline, nitrite, triphenylphosphine,cyanide, or carbon monoxide. Various commercial sources can be used toobtain the metal salts or alkoxides. A non-limiting example of acommercial source of the above mentioned metals and metal oxides isSigma Aldrich® (U.S.A.). M² and M³ are preferably provided as inorganicor organic metal salts, especially water soluble metal salts such ashalide salts, e.g., chlorides, bromides, iodides, fluorides; nitrates,nitrites, sulfates, etc. Organic metal salts may include acetates,carbonates, citrates, and the like. Preferably M² and M³ are calcium andmagnesium, and are preferably provided as the chloride salts thereof,e.g., calcium chloride (CaCl₂ and MgCl₂).

In step 2 of the method, the nanoparticles can be precipitated byreducing the pH of the aqueous solution, (for example, by introducing anacid into the aqueous solution). The acid can be an inorganic acid, anorganic acid, or mixture thereof. Non-limiting examples of suitablemineral acids include hydrochloric, nitrous, nitric, sulfuric,phosphoric acid, boric acid, hydrobromic acid, perchloric acid, nitrousacid, hydroiodic acid, and the like. Non-limiting examples of organicacids include formic acid, acetic acid, propionic acid, butyric acid,valeric acid, caproic acid, oxalic acid, lactic acid, malic acid, citricacid, benzoic acid, carbonic acid, trifluoromethanesulfonic acid,carboxylic acid and polycarboxylic acids with various functional groupsincluding phosphonate, sulfonate and the like.

In an alternative embodiment, the precipitation step can be performed byreducing the amount of alkoxide (e.g., butoxide and some water) in theaqueous solution. Reduction in the amount of alkoxide can precipitatethe nanoparticles from the solution. Removal of the alkoxide can be doneusing known removal/concentration methods, for example, evaporation atatmospheric or reduced pressure until nanoparticles are formed in theaqueous solution. In some embodiments, the alkoxide can be removed at atemperature of from 60° C. to 105° C., more preferably from 70° C. to100° C., or 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95°C., 100° C., 105° C. or any value or range there between at atmosphericpressure. In some embodiments, the alkoxide is evaporated at atemperature of 70° C. at atmospheric pressure. The precipitation stepcan for about a period of from for 0.1 hours to 48 hours, morepreferably from about 1 hour to about 24 hours, most preferably fromabout 1.5 to about 10 hours.

In step 3, the subterranean treatment additive can be loaded onto thenanoparticle using known impregnation and/or coating methods. By way ofexample, the subterranean treatment additive can be mixed with thenanoparticle to form a mixture. The mixture can be agitated (e.g.,sonicated) to form a nanoparticle having the subterranean treatmentadditive loaded therein or thereon. In a preferred aspect of theinvention, the nanoparticle can contain at least 0.1 to 70 wt. % or 80wt. %, or 0.1 wt. %, 0.5 wt. %, 1 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 20wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50 wt. %, 55wt. %, 60 wt. %, 65 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % of thewell treatment additive. Without wishing to be bound by theory, it isbelieved that the subterranean well treatment additive can be chemicalbound to the nanoparticle through an ionic bond, a covalent bond, ahydrogen bond, a Van der Walls interaction or by absorption oradsorption onto the particle. In some embodiments, the additive isloaded into the interstices of the lattice structure. In someembodiments, the nanoparticles can be separated from the anions of thesalt precursor material (e.g Cl⁻).

The additive is capable of being released from the nanoparticle in acontrolled manner over an extended period of time, e.g., for at least 10days, 1 month, 6 months, 1 year, 5 years, 10 years or 10 years. Inparticularly preferred embodiments, at least some of the additive isreleased for at least 2000 days after application.

C. Subterranean Well Treatment Compositions

The loaded nanoparticles of the present invention can be provided to atreatment site as individual nanoparticles or as a subterraneantreatment composition (e.g., a subterranean well treatment composition).By way of example, a subterranean well treatment composition can includea fluid (e.g., an aqueous liquid) that contains a plurality of loadednanoparticles (e.g., a slurry). The composition can be acontrolled-release composition capable of releasing the subterraneantreatment additive over an extended period of time. These compositionscan be prepared by admixing the loaded nanoparticles of the inventionwith a fluid that will be injected into the well. Non-limiting examplesof a subterranean treatment composition fluid include water, salt water(KCl) an acidic aqueous solution, low sulfate seawater, an aqueoussodium carbonate solution, a surfactant, or other flush fluid, or can bea nonaqueous fluid (e.g., based on oil, natural gas or petroleum basedfluids), or can be a combination of nonaqueous and aqueous fluids.

D. Methods of Treating Subterranean Wells or Wellbores

The loaded nanoparticles or loaded nanoparticle composition can bedelivered to the subterranean formation using a variety of methods,pumping, pressuring injection, or the like. In some embodiments, asqueeze or continuous treatment method is used. A method of treating asubterranean formation, well, or wellbore is depicted in FIG. 1 . Inaddition to treating wells, the loaded nanoparticles can be used todeliver additives to the subterranean formation for other purposes(e.g., deliver mud additives to drilling fluids or enhanced oil recoveryfluids, or the like). Wells 102 can intersect the subterraneanformation, and can be injection wells, production wells, water wells, orthe like. As shown, the wells 102 intersect as vertical wells, but canbe horizontal wells. Wells 102 can be uncased wellbores, cased wellboresor the like. In method 100, prior to production from well 102, theloaded nanoparticles or composition of the present invention can beinjected into one or more wells 102, flow through the well and intosubterranean formation 104 as shown by arrow 108. The loadednanoparticles 110 can be deposited on rock formation 106 in thesubterranean formation. Known drilling equipment (e.g., oil, gas, orwater drilling equipment) can be used to inject the subterranean welltreatment compositions into wells 102 (e.g., using a squeeze method,continuous method, or spear method). The nanoparticles can adsorb to theformation rock 106 and be the additive loaded on the nanoparticle can bereturned to the well 102 in an amount effective to perform the necessaryfunction (e.g., inhibit scale) when the well is put into production. Asshown in the FIG. 1 , fluid can flow over the rock as shown by arrow 112and dissolve or desorb a small amount of treatment additive from thenanoparticle. The formation fluid containing the treatment additive thenflows into the well. The treatment additive can coat or interact withthe well materials or fluid in the well to treat the well (e.g., inhibitscale). By way of example, the treatment additive can be a scaleinhibitor and contact of the formation fluid with the scale inhibitordissolves or desorbs an effective amount of the scale inhibitor from thenanoparticle and carries the scale inhibitor into the well. The scaleinhibitor can interact with the well material and/or fluids in the wellto inhibit scale from forming on the inside portion of the wall of well102. The composition of the nanoparticle and adherence of the additiveto the nanoparticle allows an effective amount of additive to bereleased from the nanoparticle over an extended period of time (e.g.,greater than 5 years).

EXAMPLES

The present invention will be described in greater detail by way ofspecific examples. The following examples are offered for illustrativepurposes only, and are not intended to limit the invention in anymanner. Those of skill in the art will readily recognize a variety ofnoncritical parameters which can be changed or modified to yieldessentially the same results.

Example 1 Nanoparticle Preparation

Nanoparticles according to the present invention can be prepared using aprecipitation method.

Magnesium chloride (0.18 g, MgCl₂, Sigma Aldrich® (U.S.A.)) and calciumchloride (0.18 g, CaCl₂, Sigma Aldrich) were dissolved in deionizedwater (180 mL) to form a 0.1 wt./vol. % by solution. The magnesiumcalcium chloride solution was heated to 90° C., and aluminumtri-sec-butoxide (25.4 g, Al(sec-BuOH)₃, Sigma Aldrich® (U.S.A.)) wasadded to above Mg/Ca salt solution to form a 3 wt. % Al/Mg/Ca colloidsuspension. The Al/Mg/Ca colloid suspension was stirred for an hour at90° C., and then any volatile by-products (e.g., residual alkoxide andsalts thereof) were evaporated by stirring the solution in an opencontainer for approximately 3 hours at 90° C.

The pH of the Al/Mg/Ca colloid solution was adjusted to 4 by addition ofnitric acid (0.4436 mL, 70%, Fisher Scientific, (U.S.A)). At or aroundpH of 4, the aluminum/magnesium/calcium nanoparticles have a highlypositively surface charge, which dispersed themselves in the slurry toform stable colloids. The slurry was allowed to cool to roomtemperature, and the sulfonated polycarboxylic acid (SPCA) scaleinhibitor (5 g, Nalco Champion (U.S.A.) EC6157A) and deionized water (15mL) was added to 40 mL of the 3 wt. % the slurry. The SPCA/nanoparticleslurry was sonicated for 1 minute with a sonicator that delivered 55watts using 3371 joules over 1 minute to provide the loadednanoparticles of the present invention (e.g., SPCA loaded[Al₁Mg_(0.02)Ca_(0.02)]OOH nanoparticles).

Example 2 Nanoparticle Characterization

Size and size distribution. Nanoparticle size and size distribution weredetermined using a laser diffraction particle size analyzer (MalvernMastersizer 3000) and by TEM imaging. Table 1 lists the size in μmetersand % volume density obtained through particle size analysis. FIG. 2depicts a graph of the size classes in μm versus volume density inpercent (%). FIG. 3 depicts a TEM image of the SPCA loaded nanoparticlesat a 100 nm scale. Arrow 301 points to the light gray uniform backgroundarea formed from the carbon tape that was used as a holder for theloaded nanoparticles during TEM imaging. Arrow 302 points to a largeaggregate of nanoparticles, arrow 303 points to a small aggregate ofnanoparticles or single nanoparticle, and arrow 304 points to the SPCApolymer surrounding the nanoparticles (darker material than background,but lighter than the nanoparticles.

TABLE 1 Size % Volume (um) Density ≤0.06  0     0.068  0.27   0.077 2.14   0.09   5.76   0.01  10.38   0.11  14.75   0.13  17.50   0.15 17.67   0.17  15.08   0.19  10.51   0.21   5.48   0.24   0.46 ≥0.28  0.00

X-ray Diffraction (XRD) Analysis. XRD analysis was performed using aRigaku DMax, 6-sample holder instrument (Rigaku Corporation, USA) Thenanoparticles from Example 1 were analyzed by X-ray diffraction methods.FIG. 4A shows XRD patterns for the Al₁(Mg_(0.02)Ca_(0.02))OOH with theAlOOH phase being identified by the square monikers and residual sodiumchloride being identified by the circle monikers. FIG. 4B show XRDpatterns for a nanoparticle of the Al₁(Mg_(0.02)Ca_(0.02))OOHnanoparticle of the present invention and a control sample absent Ca andMg. Data line 402 is the sample of the present invention, data line 404is the control sample, circles mark the peaks for AlOOH if present, andsquares mark the peaks for MgO if present. As determined from the XRD noCa(OH)₂ or Mg(OH)₂ phases were present in the nanoparticle, therebyproviding evidence that the calcium and magnesium are part of thecrystal structure. FIG. 4C is an XRD curve fit of FIG. 4B that depictsthe curve shift of the inventive sample vs. the comparative sample. Dataline 406 is the Al₁(Mg_(0.02)Ca_(0.02))OOH nanoparticle of the presentinvention and data line 408 is the comparative sample. A peak shift ofabout 49 theta was observed due to the addition of Ca and Mg.

Energy Dispersive X-ray spectroscopy (EDX) Analysis. EDX analysis wasperformed using a FEI Quanta 400 ESEM FEG (FEI part of Thermo FisherScientific, USA). The sample was made using the process of Example 1.From the EDX data it was determined that the sample has the quantitiesof oxygen, magnesium, aluminum and calcium listed in Table 2. The EDXanalysis also showed no clustering of Mg that would be associated with aseparate brucite phase (MgO_(solid)).

TABLE 2 Component Wt. % Oxygen 41% Magnesium  2% Aluminum 57% Calcium 1%

Scanning Electron Microscopy (SEM) Analysis. SEM analysis was performedusing a FEI Quanta 400 ESEM FEG. The sample was made using the processof Example 1. FIG. 5 depicts a SEM image of a layer of the dried CaMgnanoparticle. From the EDX data it was determined that the sample hasthe quantities of oxygen, magnesium, aluminum and calcium listed inTable 2.

Thermodynamic Analysis. Thermodynamic analysis was done to show nooxides were present in the nanoparticle. Initially, aluminumtris(sec-butoxide), Al(OBu)₃, is added to 90° C. hot water to a finalconcentration of 0.56 M. As Al(OBu)₃ reacts, the pH increases to around9 pH. The overall reaction is:

${{{Al}({OBu})}_{3} + {3H_{2}O}}\overset{{heat}{and}{stirring}}{\rightarrow}{{\gamma AlOOH}_{boehmite} + {3{HOBu}}}$

Some butanol was lost to the atmosphere, during synthesis. Withoutwishing to be bound by theory it is believed that the hydrolysis shouldhave little effect on the pH, but probably due to slow kinetics as one,two, and then three of the aluminum butoxide bonds are hydrolyzed theremay be an intermediate increase in solution pH. The observed pH valueincreased to around 9 pH at 90° C. Then calcium and magnesium chloridewere added along with concentrated nitric acid until the final pH wasabout 4 pH. Then the sample was heated for two more hours at 4 pH.Nearly all of the aluminum precipitated as γAlOOH_(boehmite) solid, asconfirmed by XRD. Furthermore, γAlOOH_(boehmite) will remain virtuallyinsoluble to below 4 pH.

FIG. 6 is a plot of a simulation of boehmite and brucite (MgO_(solid))solubility vs. pH from 9 to 4 pH at 90° C., done using Visual Minteq 3.0software (KTH, Sweden). FIG. 6 shows plots of initial and final Total Alconcentration (M) vs. pH, assuming boehmite as possible precipitation,and total Mg vs. pH, assuming brucite as possible precipitation at 90°C. From the simulation, it was determined that brucite can precipitatefrom about 7.5 to 9 pH, but as the pH was lowered to below approximately7.5 pH, it dissolved. Thus, it was determined that at the reactionconditions of 4 pH and 90° C. for two hours there is no reasonablepossibility for brucite to remain in the solid phase. The absence ofbrucite was also confirmed by EDX analysis showing noconcentrations/clustering of Mg, that would be associated with aseparate brucite phase, rather the Mg was uniformly distributed in thesolid phase. This material has been used with SPCA and shows enhancedperformance over the product without Mg in the solid.

Example 3 Release Performance of Scale Inhibitor

Release performance was measured in reservoir material by injecting thenanoparticles from Example 1 or a comparative sample (SPCA alone(“SPCA”) into the core material and then flowing simulated producedwater back through the same reservoir material. The release rate wasdetermined by the concentration of the loaded nanoparticles of thepresent invention or SPCA over time. FIG. 7 depicts a graph of SPCA andthe loaded nanoparticles of the present invention concentration returnsas translated to production days. Data line 700 is the loadednanoparticles of the present invention and data line 702 is SPCA. Fromthe data, it was determined that the loaded nanoparticles of the presentinvention provided controllable release of the additive over an extendedperiod of time that was at least 5 times longer than the conventionaladditive.

The invention claimed is:
 1. A mixed metal oxide nanoparticlecomprising: M¹ _(x)O_(n)H_(m); M² _(y)O_(n)H_(m); and M³ _(y)O_(n)H_(m),where M¹, M², and M³ are each in the crystal lattice structure of thenanoparticle, M¹ is a Column 13 element selected from aluminum (Al),gallium (Ga), indium (In), and thallium (Tl), M² and M³ are eachindividually a Column 2 metal, a Column 14 metal, or a transition metal,with the proviso that M² and M³ are different, and x is 0.03 to 3, y is0.01 to 0.4, z is 0.01 to 0.4, and n and m for each of M¹_(x)O_(n)H_(m), M² _(y)O_(n)H_(m), and M³ _(y)O_(n)H_(m) is individuallydetermined by the oxidation states of the metals M₁, M₂, and M₃.
 2. Themixed metal oxide nanoparticle of claim 1, wherein M₂ and M₃ are eachindependently beryllium (Be), magnesium (Mg), calcium (Ca), strontium(Sr), barium (Ba) and radium (Ra).
 3. The mixed metal oxide nanoparticleof claim 1, wherein M₁ is Al, M₂ is Mg, and M₃ is calcium (Ca).
 4. Themixed metal oxide nanoparticle of claim 1, wherein the nanoparticle hasa diameter of 1 nm to 10,000 nm.
 5. The mixed metal oxide nanoparticleof claim 4, wherein the nanoparticle has a diameter of 10 nm to 1000 nm.6. The mixed metal oxide nanoparticle of claim 5, wherein thenanoparticle has a diameter of 10 nm to 200 nm.
 7. The mixed metal oxidenanoparticle of claim 1, wherein the nanoparticle further comprises anadditive.
 8. The mixed metal oxide nanoparticle of claim 7, wherein theadditive is capable of being released from the nanoparticle in acontrolled manner over an extended period of time.
 9. The mixed metaloxide nanoparticle of claim 7, wherein the well treatment additive ischemically bound to the nanoparticle through an ionic bond, a covalentbond, a hydrogen bond, a Van der Walls interaction, or by adsorptiononto the particle.
 10. The mixed metal oxide nanoparticle of claim 7,wherein the nanoparticle is impregnated with the additive.
 11. The mixedmetal oxide nanoparticle of claim 7, wherein the nanoparticle furthercomprises a coating, and wherein the additive is comprised in thecoating.
 12. The mixed metal nanoparticle of claim 7, wherein theadditive is a scale inhibitor, a hydrate inhibitor, a clay stabilizer, abactericide, a salt substitute, a relative permeability modifier, asulfide scavenger, a corrosion inhibitor, a corrosion inhibitorintensifier, a pH control additive, a surfactant, a breaker, a fluidloss control additive, an asphaltene inhibitor, a paraffin inhibitor, achelating agent, a foamer, a defoamer, an emulsifier, a demulsifier, aniron control agent, a solvent, or a friction reducer, or any combinationthereof.
 13. The mixed metal oxide nanoparticle of claim 12, wherein theadditive is a scale inhibitor.
 14. The nanoparticle of claim 13, whereinthe scale inhibitor is an organic molecule having a carboxylic acid, apolycarboxylic acid, aspartic acid, maleic acid, sulfonic acid,phosphonic acid, or a phosphate ester group or salts thereof.
 15. Thenanoparticle of claim 14, wherein the scale inhibitor is a polymercomprising sulfonated polycarboxylic acid functionality.
 16. The mixedmetal oxide nanoparticle of claim 12, wherein the additive is anasphaltene inhibitor.
 17. The mixed metal oxide of claim 7, wherein theadditive is a subterranean treatment additive.
 18. The mixed metal oxidenanoparticle of claim 17, wherein the additive is a well treatmentadditive.
 19. The mixed metal oxide nanoparticle of claim 2, wherein thenanoparticle comprises at least two additives, and wherein the at leasttwo additives are different from each other.
 20. A compositioncomprising a plurality of the nanoparticles of claim
 1. 21. Thecomposition of claim 20, wherein the composition is a fluid.
 22. Thecomposition of claim 20, wherein the composition is an aqueous liquid,and wherein the plurality of nanoparticles are suspended within theaqueous liquid.
 23. The composition of claim 20, further comprisingwater.